As is well known in the art, treatment of various medical conditions commonly involves implantation of medical devices and prostheses into a body. Illustrative is the implantation or deployment of a vascular prosthesis, e.g., endograft or stent device, into a cardiovascular vessel, e.g. vein or artery, to treat and/or repair a diseased or damaged region therein.
As is also well known in the art, vascular prostheses, i.e. stents, are often employed to provide an artificial conduit proximate a diseased or damaged vessel region in and/or maintain an open passageway through a cardiovascular vessel. Such vascular prostheses can be designed for temporary placement, i.e. to maintain the patency of the vessel, or permanent placement.
There are, however, several drawbacks and disadvantages associated with conventional vascular prostheses. A common problem associated with implantable vascular prostheses is intimal hyperplasia after intervention in the vessel, such as a coronary artery. Indeed, it has been found that a significant percentage of arterial bypass grafts and vein grafts fail due to intimal hyperplasia after coronary bypass surgery. Endothelial denudation, platelet adherence, and leukocyte infiltration are some of the functions that can contribute to the proliferation of vascular smooth muscle cells in the vessel and subsequent onset of arterial stenosis.
Further, many conventional vascular prostheses; particularly, stents are often constructed from various polymeric materials, such as poly(ethylene terephthalate) (PET). Such prostheses often cause irritation and undesirable biologic responses from the surrounding tissues in a vessel.
Although conventional vascular prostheses are designed to be implanted for an extended period of time, it is sometimes necessary to remove the device prematurely, for example, because of poor patency or harsh biological responses. In such instances, the device generally must be removed through a secondary surgical procedure, which can, and in many instances will, result in undesirable pain and discomfort to the patient and possibly additional trauma to the vessel tissue. In addition to the pain and discomfort, the patient must be subjected to an additional time consuming and complicated surgical procedure with the attendant risks of surgery.
More recently, bioabsorbable and/or biodegradable prostheses have been developed in an effort to eliminate the harsh biological responses associated with conventional polymeric and metal vascular prostheses. There are, however, several known disadvantages associated with bioabsorbable and biodegradable prostheses.
One major disadvantage is that the bioabsorbable and biodegradable materials and, hence, prostheses often break down at a faster rate than is desirable for the application. A further disadvantage is that the bioabsorbable and biodegradable materials can, and in many instances will, break down into large, rigid fragments that can cause obstructions in the interior of a vessel.
A further disadvantage associated with conventional vascular prostheses is that existing means for securing the prosthesis into or onto biological tissue within a body vessel have had limited success. Often the securing means comprises engaging the prosthesis to the surrounding tissues by physical or mechanical means, such as disclosed in U.S. Pat. No. 7,918,882. Another securing means comprises modifying the prosthesis surface or material to induce the production of fibrous (scar) tissue to anchor the prosthesis upon implantation within the vessel.
There is thus a need to provide improved vascular prostheses that substantially reduce or eliminate (i) intimal hyperplasia after intervention in a vessel, (ii) the harsh biological responses associated with conventional, and (iii) employ effective vessel securing means.
There is also a need to provide vascular prostheses that can replace or improve biological functions or promote the growth of new tissue in a subject.
There is also a need to provide vascular prostheses that substantially reduce or eliminate the formation of inflammation and infection.
There is also the need to provide vascular prostheses having mechanical compatibility or enhanced mechanical properties. As is well known in the art, a mismatch between the stiffness, hardness, and porosity of a prosthesis in comparison to the surrounding tissue environment can cause irritation and other complications after implantation.
It is therefore an object of the present invention to provide vascular prostheses that substantially reduce or eliminate (i) intimal hyperplasia after intervention in a vessel, (ii) the harsh biological responses associated with conventional polymeric and metal prostheses, (iii) employ effective vessel securing means, and (iv) the formation of biofilm, inflammation and infection.
It is another object of the present invention to provide vascular prostheses that can effectively replace or improve biological functions or promote the growth of new tissue in a subject.
It is another object of the present invention to provide vascular prostheses that include effective anchoring means for positioning the prostheses proximate target tissue.
It is another object of the present invention to provide vascular prostheses that can administer one or more pharmacological or therapeutic agents to a subject.
It is another object of the present invention to provide vascular prostheses having optimum mechanical compatibility with vascular structures.